Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 11-21-2018, 07:04 AM
85 DSEL's Avatar
Documented User
 
Join Date: Oct 2006
Location: Dayton, Ohio
Posts: 1,023
M103 Sensors

Trying to sort out the sensors that are located on top of the head near the valve cover. What are each of these and their respective function?

One sends signal for the dash temp gauge, another monitors coolant temp, but what each of them does I am not certain. Any clarification offered will be appreciated

Dale
__________________
1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
Reply With Quote
  #2  
Old 11-21-2018, 10:50 AM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,058
Thumbs up

Front by the oil port is some thermo vacuum switch. It opens or closes after a certain temp. You would have to trace the lines to see where they run, maybe the evaporative emissions stuff.

Single pole is the sensor for gauge cluster.

The two pole by the breather I think is the aux fan trigger.

Rear should be for the ECU.



Been a while since I have been up close with an early M103 layout
__________________
I'm not a doctor, but I'll have a look.

'85 300SD 244k
'87 300SDL 251k
'90 300SEL 325k
'91 560SEL 189k

Eight others from IH, BMW, GM, Ford, and Volvo.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
  #3  
Old 11-21-2018, 12:30 PM
Registered User
 
Join Date: Aug 2006
Posts: 717
The one closest to the firewall is a dual thermistor with the case as the common ground. One temperature sensor is for the ECU and the other goes to the ignition module.

Later models used a 4 pin sensor that had 2 ground wires so it did not depend on the case making a good ground with the head.
Reply With Quote
  #4  
Old 11-21-2018, 01:39 PM
85 DSEL's Avatar
Documented User
 
Join Date: Oct 2006
Location: Dayton, Ohio
Posts: 1,023
Thanks for your input!


Any chance that one of these has a direct affect on when the climate control *should* begin functioning after it has sat overnight? I'm trying to figure out *why* the climate control sometimes starts 'blowing' as soon as I start it up to pull out of the garage and other times not....thinking it could be a coolant temp sensor on the block. Could be wrong - probably am


Dale
__________________
1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
Reply With Quote
  #5  
Old 11-21-2018, 05:45 PM
Registered User
 
Join Date: Aug 2006
Posts: 717
The one with the blue tape on the wire is for the climate control.

Resistance values as of 09/87:

5.0 - 8.0 k ohm @ 20 degree C
900 - 1800 ohm @ 60 degree C
460 - 650 ohm @ 85 degree C
300 - 400 ohm @ 100 degree C

You should be able to pull codes from pin 7 of the diagnostic connector near the battery.
Reply With Quote
  #6  
Old 11-21-2018, 09:45 PM
85 DSEL's Avatar
Documented User
 
Join Date: Oct 2006
Location: Dayton, Ohio
Posts: 1,023
M103 Sensors

Quote:
Originally Posted by Rick76 View Post
The one with the blue tape on the wire is for the climate control.



Resistance values as of 09/87:



5.0 - 8.0 k ohm @ 20 degree C

900 - 1800 ohm @ 60 degree C

460 - 650 ohm @ 85 degree C

300 - 400 ohm @ 100 degree C



You should be able to pull codes from pin 7 of the diagnostic connector near the battery.


Thanks Rick for this info. I'll need to dig out my tester I made several years ago and relearn how to set it up!

A *dumb* question: will I need to remove the sensor from the head to test or can it be tested in place? I'm guessing in place...

Dale
__________________
1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
Reply With Quote
  #7  
Old 11-22-2018, 03:35 AM
Registered User
 
Join Date: Aug 2006
Posts: 717
Just unplug it and check with an ohmmeter between the 2 pins.
Also check to ground, which should be infinite resistance.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 09:30 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page